4l80e transmission trouble

Just had transmission rebuilt. Thinking the problem was the old transmission ,not so. It seams I have electrical problems causing the transmission to shift hard. It also will have a hard time shifting from 3rd gear to over drive.This does not happen all the time, some times i can go several days without any problems.Mechanics at transmission shop says it bad grounds.I dont know ! Can someone please help!!!I know the mechanics are doing all they can, and havent charged me for any additional charges with these problems. :screwy:

ttt

What year? Does the check engine light come on?

I have heard that a bad ignition switch can cause the wrong voltage at the tranny causing shifting problems.

//2000CAYukon

Bad ignition switch is possible does the tach go wacky when this happens? could be grounds,wiring,output sensor

Troy1
I was going to Lubbock to return to the Tranny shop and going over the over pass it went from 2500 rpm to 3500 rpm within a few seconds.It ocassionally will show a check engine light.but not always.It seams when i am going to have trouble the engine wont idle down at start up.